The 36 women from St Helens, Merseyside, could now be awarded compensation of up £10,000 each, according to their union, the GMB.

The House of Lords held that St Helens Council, which had written letters to the women pointing out that they might be responsible for the loss of their colleagues’ jobs if they won their equal pay claims, had effectively threatened them.

The dinner ladies were among 500 workers, including a group of male road sweepers, who brought an equal pay claim against St Helens Borough Council in 1998.

Brian Strutton, GMB national secretary for public services, said: “[The women] were made to feel they would be personally responsible for the council’s claimed financial difficulties if they were successful.

“It was extremely distressing to be told by their employer that their action might lead to cuts, to children going hungry at lunchtime, to colleagues losing their jobs or not receiving pay rises.”

St Helens Council said: “This issue is part of the national debate on equal pay in the public sector and goes back to 1998. St Helens was one of the first councils to fulfil its obligation in terms of settling equal pay claims and liabilities.”